immense delayed write to file system (ZFS and UFS2), performance issues

[Jeremy Chadwick]

On Tue, Jan 19, 2010 at 10:28:58AM +0100, Morgan Wesström wrote:
> Garrett Moore wrote:
> > The drives being discussed in my related thread (regarding poor performance)
> > are all WD Green drives. I have used wdidle3 to set all of my drive timeouts
> > to 5 minutes. I'll see what sort of difference this makes for performance.
> > 
> > Even if it makes no difference to performance, thank you for pointing it out
> > -- my drives have less than 2,000 hours on them and were all over 90,000
> > load cycles due to this moronic factory setting. Since changing the timeout,
> > they haven't parked (which is what I would expect).
> 
> You're welcome. I just feel as bad for you as for everyone else who has
> bought these obviously Windoze optimized harddrives. Unfortunately
> neither wdidle3 nor an updated firmware is available or functioning on
> the latest models in the Green series. At least that's what I've read
> from other people having this issue. WD only claims they don't support
> Linux and they probably have never heard of FreeBSD.

No offence intended by this statement, but: the Green drives are
specifically intended for workstations.  I don't believe in the whole
"segregation of drive model" thing, but the fact of the matter is, the
Green drives are variable-RPM and have numerous firmware-level features
which intend for them to be used in workstation environments -- that
means not constant I/O or heavy workload.  Windows has nothing to do
with this.

If you want a consumer-edition drive that's better tuned for server
work, you should really be looking at the WD Caviar Black series or
their RE/RE2 series.  I have both the Green and Black drives, and I've
done my share of benchmarking.  Sustained transfer rates on the Black
models exceed that of the Greens by almost 20-25MB/sec.  Average seek
times are slightly lower, and I/O concurrency is handled much better.

The Black drives also have a feature called TLER[1], which can be
toggled using a utility from Western Digital.  Those using these drives
in a RAID or ZFS array will be very interested in disabling this feature
to ensure quick timeouts from the drive in the case of I/O errors.
Other manufacturers have the same feature, just called something else
(ex. Samsung's is called CCTL).

Now, admittedly WD doesn't give this utility out any more (which is
silly), and some people have reported that recent-day (circa mid-to-late
2009) Black drives refuse to let you toggle TLER.  The latter claim is
absurd -- I purchased 4 Black drives (2 with manufacturing dates of
October 2009, and 2 with September 2009) and all of them let me toggle
TLER without any problem.  Keep in mind you your SATA controller has to
be set to non-AHCI mode (sometimes called "Enhanced mode") or
Compatibility mode (e.g. IDE emulation) for the utility work.

If you have qualms/concerns/issues with Western Digital drives or their
mentality behind their drives, simply don't buy them.  Really.  People
often ask me (and others) "what brand of hard disk is good?" and I
always tell them the same thing: "there's no correct answer.  Everyone
has their own experience with different vendors, models, etc."

[1]: http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery

> If anyone successfully has fixed their WD15EADS drives this way I'd be
> interested in hearing from you. One of my drives has 216,000 load cycles
> accumulated over 8 months. That's one every 2nd minute... and I was hit
> by the Seagate 7200.11 fiasco too. Running on Samsungs now :-)

Aren't Samsung's drives known for firmware bugs/quirks?  The
documentation associated with smartmontools discusses this quite a bit.
This is one reason why I stay away from them.  Fujitsu is another vendor
I want absolutely nothing to do with (very high failure rates in
addition to bad sectors with their SCSI-3 disks at my workplace).

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |